1. Technical Field
The present invention relates to a displaying technique of a digital projection, especially to a displaying method of DLP and a DLP projector.
2. Description of the Related Art
DLP projector becomes to be one of the mainstream digital projectors, and the imaging principle is illustrated as follows. Referring to FIG. 1, the projector 100 includes an illuminating system 110, a light modulation device 120 and a projection lens 130. The light modulation device 120 includes a driver printed circuit board (PCB) 121, and a digital micromirror device (DMD) 122 disposed on the driver PCB 121. The DMD 122 has a predetermined light incident direction. The light system 110 includes a light source 112, a light rod integrator 113, a plurality of condenser lenses 114 and a reflection mirror 116a. After the illumination light beam 112a emitting from the light source 112, the illumination light beam 112a passing through the rob integrator 113 and the condenser lenses 114 is reflected by the reflection mirror 116a, and is incident to the DMD 122 along the predetermined light incident direction, thereby the DMD 112 modulates the illumination light beam 112a to an imaging light beam 112a′, and reflects the imaging light beam 112a′ to the projection lens 130. Then the projection lens 130 will project the image beam 112a′ to a screen (not shown) for displaying image.
Referring to FIG. 2, the DMD 122 includes a plurality of bistable micromirrors 123. Each micromirror 123 represents a pixel or a sub-pixel. The bistable micromirror 123 has two different oblique angle states, for instance, the oblique angle is at plus 12 degrees in a first stable state, and at minus 12 degrees in a second stable state. When the illumination light beam 112a is incident on the DMD 122 along the predetermined light incident direction thereof, the micromirror 123 in the first stable state (a solid line shown in FIG. 2) reflects the light beam to the projector 130, and the micromirror 123 in the second stable state (a broken line shown in FIG. 2) reflects the light beam to a direction different from the direction to the projector 130. At this point, the first stable state is a light on-state; and the second state is a light off-state.
The predetermined light incident direction of the DMD 122 depends on a manufacture process and a driver wafer of the DMD 122. Generally, the manufacturers of the DMD mark a recognizing pattern on the DMD for facilitating the assembly workers to recognize the predetermined light incident direction, such as the recognizing pattern 112a of the DMD 122 shown in FIG. 1.
When a state of one of the micromirrors fails to be controlled by the digital imaging signal, this micromirror is a defect dot. The defect dot can be classified as two types, the micromirror continuously in on-state is defined as bright defect dot, and the micromirror continuously in off-state is defined as dark defect dot. Usually, the dark defect dot may not to be easily recognized by a viewer, thereby a few of dark defect dots are allowed, but the bright defect dot may easily be recognized by a viewer since it may induce the optical discomfort. Therefore, in advantage, the bright defect dot is not allowed.
When the illumination light beam 112 is incident along the predetermined light incident direction of the DMD 122, if the DMD 122 has bright defect dot, the product must be abandoned because it fails to conform a delivery standard. Thus, a manufacturing yield rate of the projector will be lowered. To some extents, the manufacturing cost will be increased.